. >> it takes no energy. >> and do what my mother always told me, write your thank-you letters. >> peter greenberg going out on a limb. thank you very much. >>> two weeks ago we reported on a case of jon hammar, a marine veteran who was locked up in mexico for four months. he's on his way home for christmas. as jim axelrod reports the return trip has not been easy. >> reporter: when he crossed over the border into the u.s. friday night it seemed like jon hammar's four-month ordeal was over. hammar had been in a mexican jail since august for bringing a shotgun across the border for a surfing vacation with a friend. he was held in a notorious prison said to be run by a drug cartel. and in this photo he's actually chained to a bed. >> we actually started receiving calls from members of the cartel saying, you know, we have your son and we're going to kill him. and they put him on the phone and i realized they really did. >> to make matters worse he was suffering from post-traumatic stress disorder after serving tours in iraq an afghanistan. after getting nowhere with the authorities they wen